The present invention relates generally to the production and processing of elastane filaments and, more particularly, to a method for selectively altering physical properties, especially denier, elongation and tenacity, of such filaments.
Elastane filaments, sometimes more commonly referred to in the textile industry as spandex filaments, are highly elastic synthetic fibers well known and commonly used throughout the textile industry, particularly for imparting a desired degree of elasticity to textile fabrics. As is well known, elastane filaments are essentially comprised of linear macromolecules primarily of segmented polyurethane, either polyetherurethane or polyesterurethane. Such elastane filaments are known to be produced by several differing spinning processes commonly referred to as dry spinning, wet spinning, reactive spinning and melt spinning.
Regardless of the precise chemical composition and the method of manufacture of an elastane filament, such filaments characteristically exhibit a very high degree of longitudinal elongation to breakage of several hundred percent, typically between four hundred and eight hundred percent of the relaxed longitudinal dimension of the filaments, with the ability to substantially completely recover from such elongation repeatedly (e.g. 95% to 98% recovery). Thus, as indicated, elastane filaments are uniquely and advantageously suited to use in textile fabrics, e.g., apparel fabrics, wherein a degree of stretchability is desirable to enhance the functionality and usability of such fabrics.
As used herein, the term "elastane" is accordingly intended to have the broadest interpretation and scope in accordance with conventional textile industry usage so as to encompass any and all filaments and fibers of the type afore-described, whether now known or subsequently developed. Reference may be had to the Manmade Fiber Year Book (CFI), Second Issue, 1995, at pages 30-40, for a more detailed technical description and understanding of elastane filaments and fibers, which work is incorporated herein for reference purposes.
Whether elastane filaments are produced by any of the known manufacturing processes of dry, wet, reactive or melt spinning, the physical properties of the filaments thusly produced are conventionally considered to be suitable for immediate use in textile fabric forming operations without the need for, or any perceived benefit from, subsequent processing. In contrast, with certain other types of extruded synthetic filaments used in the textile industry, most notably polyester and nylon, conventional wisdom and experience holds that, before such filaments are suitable for use in the manufacture of textile fabrics, manipulation of the physical characteristics of the filaments is necessary through a drawing operation, including heat setting in the case of polyester filaments, in order to improve and stabilize molecular orientation within the filaments. Such drawing and heat setting of polyester, nylon and like filaments is known to be performed either on a single filament, e.g., through a draw twisting or like process, or on multiple filaments simultaneously, e.g., in a so-called draw warping process predominantly utilized to prepare the filaments for use in weaving or warp knitting of a textile fabric.
Heretofore, drawing and heat setting of elastane filaments, whether performed on a single filament or multiple filaments, is not known to have been utilized or even attempted in the textile industry and it is believed that conventional wisdom holds that no particular benefits would result since, in contrast to polyester and nylon filaments, the molecular structure within such filaments is stable in the state of the filaments exiting the spinning process and the attendant physical characteristics of the filaments as so produced are already well suited to textile fabric applications without further processing.